NorNed Interconnector Project connects the Netherlands and Norway. (Credit: TenneT)
NorNed was built with an investment of around €600m. Image Representative. (Credit: J. Lindsay/Wikipedia)
NorNed cable terminal in Eemshaven. (Credit: jbdodane/ Flickr)

The NorNed Interconnector Project is a 580km-long subsea High Voltage Direct Current (HVDC) transmission cable that connects the Netherlands and Norway.

The interconnector is the longest under-water high-voltage cable developed as a joint project by the Dutch transmission system operator TenneT and Norwegian counterpart Statnett.

NorNed was built with an investment of around €600m. It began operations in 2008 and has a transmission capacity of 700MW.

In May 2022, operations were suspended after a cable failure. The interconnector resumed operations in October 2022 following repair work. However, the capacity was reduced to 620MW to reduce stress on the cable.

The cable is used to transfer electricity to and from Norway and the Netherlands, ensuring greater power security in the two countries. The development of the interconnector is also aligned with the European Union’s (EU) policy to integrate markets.

NorNed Interconnector Route

The NorNed Interconnector Project stretches from Feda in Norway to Eemshaven in the Netherlands via the North Sea. There are two converter stations, at Feda and Eemshaven, to reduce transmission loss to less than 4%.

The maximum water depth at which the cable was laid is 420m.

HVDC technology was selected for the interconnector as it will reduce losses and help in stabilising the grid by controlling the power flow.

NorNed Interconnector Infrastructure

The NorNed Interconnector’s main circuit configuration includes a 12-pulse converter of ±450kV with the midpoint earthed and two cables. The transmission voltage of 900kV provides low cable current and reduces losses.

The converter stations, in Feda and Eemshaven, convert alternate current (AC) to direct current (DC) and after transmission to the other side from DC to AC. The AC equipment in Feda connects the 300kV AIS substation, while the AC equipment in Eemshaven connects the 380kV GIS substation via cables.

The single-phase converter transformers in both stations are of three winding types with +- 450kV twelve-pulse converters. Twelve-pulse converter has a voltage rating of 900kV. The DC voltage to ground is 450kV.

The DC cables connect both converter stations without any DC filters.

Paper-insulated type cables were used for the project. The cable system is divided into two parts- a shallow part and a deep part.

Under the deep part system, both the submarine and the tunnel cable is a MI type of cable.

The tunnel cable stretches from Feda in Norway to a jointing chamber via a 1.4km long tunnel down. Subsequently, it joins the submarine cable and runs through a 150m long micro tunnel down to the seabed around 45m under sea level.

It goes 156km out of the Fedafjord to join the single core cable.

The shallow cable, which makes up the largest part of the 580km transmission distance, is composed of single core HVDC cable and the double-core Flat Mass-Impregnated (FMI) cable.

A pair of this single core cable runs nearly 154km in up to 70m of water, while the FMI cable will run along approximately 270km of water.

A pair of 1.5km-long 790mm single-core land cables, which stretch from the FMI landfall to the converter station in Eemshaven, are also part of the cable network.

In Norway, the AC system consists of strong transmission lines going west to east to areas around Oslofjord. In the Netherlands, the AC network in Eemshaven connects the converter station.

Two generators connect the 380kV Eemshaven substation beside the HVDC converter. The 380kV substation is connected to the adjacent 220kV substation next to the two transformers of 220kV/380kV and 750MVA rated power.

The Eemshaven substation is connected to the main 380kV network by a four circuit 380kV line.

Key Contractors

In 2000, ABB received a $270m contract from TenneT and Statnett for the NorNed Interconnector Project. As per the contract, ABB delivered HVDC converter stations and the majority of the underwater power cables.

The deep part of the cable system was delivered by Nexans Norway, while the shallow part was supplied by ABB.

HI-RES Subsea Services was selected to install the largest HVDC interconnector in the world.

Hitachi Energy supplied two converter stations and the cable system for the major portion of the subsea cable system of the project.

NorNed Financing

Nordic Investment Bank provided €100m loan for the development of the NorNed Interconnector Project.

European Investment Bank financed nearly 50% of the project.